The website FlightAware, with locations in Houston, Texas and Singapore, is the world's largest flight tracking data company and provides over 10,000 aircraft operators and service companies as well as over 12,000,000 passengers with global flight tracking solutions. FlightAware gets data from air traffic control systems in over 55 countries. FlightAware provides live flight data, airport delays, fuel prices, airline operational tools, weather maps, flight planning, flight routes, oceanic tracks, and navigation charts, as well as aviation news and photos.
These are fun sites to visit if, for example, you want information about that plane flying overhead. Just go to the site, zoom in on your location, and click on the plane's icon. You will get information on the company, the call sign, the plane's origin and destination, altitude and air speed. Another good site is Plane Finder.
Aviation Weather is a US government site located near the Kansas City International Airport that allows you to access just about anything you want to know about weather conditions pertaining to aviation.